black pipe assembly technique

I am helping my plumber do some of the work on my house, under his supervision
and I'm good with PEX and copper, but can't seem to get the hang of black iron
using Gasoila on first 3 threads, not too much, well-seated into threads, and tightening 'not too tight' (my plumber's instruction)
but I think his idea of not too tight and mine are quite different
redid some of the boiler trim and on pressurizing (only 15 psi) had drips at most of the unions
so I am thinking I need to go WAY tighter
maybe he means not gorilla tight
the only tip I've found online is 'hand-tight and then 1.5 extra turns w/ a wrench'
which is pretty close to what I was already doing
(maybe not quite 1.5)
but how do you go 'hand-tight' with a short nipple, for example? if one thread catches slightly, you're 'hand-tight' but not anywhere near 'sealed'
I'd raher have torque recommendations for 1/2", 3/4", 1" etc
or some other benchmark for how fully to apply the wrench

Hand tight + one wrench turn is a rule for plastic pipe. It is not tight enough for black pipe. The link below shows the thread engagement , hand turns + wrench turns for various sizes of pipe. What size are you using? And you mentioned unions.....is it the union joint that is leaking, or the threaded pipe connection to the union fitting.?

Gas is not water. Gas kills and having a gas leak on a gas line you just touched will scare the hell out of your customer whether it is a seepage leak or not. You'll lose that customer forever as well because they'll think you endangered thier life.

I crank them till they stop. You can always tell if black iron was threaded by a new or old die. Old die usually means the pipe is going to travel all the way to the end. Newer will have that connection 3 to 4 threads deep.

I take no chances on black iron because I know those systems over years start to leak from all the vibrations of the structure, causing the threads to allow leaks. I get calls from the utility company from customers stating the gas was just shut off and they found 13-20 leaks in the gas lines.

if you depend on hand tight with any specific number of turns with a wrench, you WILL have leaks. Properly adjusted sharp dies cut proper threads, but if they are not adjusted correctly they will either cut tight or loose theads and your "rule" will no longer work, even it it ever did. Old dies cut tighter threads because they are getting worn, so those will need more tightening that newer ones.

thanks for the tips
according to the chart, 4.5 hand turns + 3 wrench turns is standard for both 1/2" and 3/4" black pipe
that is probably more than I was doing, and may have been more than I am capable of doing
I will count next time (I might have been doing more hand turns than I think)
reassembled boiler trim yesterday going considerably tighter
I also used a combination of teflon tape and Gasoila soft-set sealant (talked to Gasoila and that is what they recommended for problem joints)

I think part of the problem is that my plumber put together the trim with a mix and match of what came with the boiler, his own odds and ends, and new stuff from the supply house
so unlikely that any two pair of threads was matching up perfectly

but it sounds like you are all pretty much saying go as tight as you can, that there is danger going too loose, but not a danger going too tight
why did my guy say 'not too tight' ??

I should have also mentioned to read the note that accompanies that thread chart I linked to. They ackowledged that field cut threads, and often even factory cut threads, do not have the full length of threads called out, and hence the variation in the turns required for "tight". I think we are all in agreement that you probably did not get it tight enough, because 3/4" pipe with for example a 12" wrench would take considerable effort to get tight. Unless you have arms like Mighty Joe Young an 18" wrench would not be too big!

I use a 10" wrench on 3/4". An 18" wrench is WAY, WAY too big, unless you are a 98# weakling and need the Charles Atlas body building set. Do not spend any time following a chart as to "generic" threads. Just use some common sense. My wife's uncles put the waterers in for a dairy barn once. Since it was modular they precut the system, using the standard calculation for make up. Then they went in for dinner while the farmer's sons put the pipes together. Since the sons were built like 600# gorillas they tightened the pipes until there were no threads showing. By the time they reached the last waterer, the openings were 3" short from where they should be. The entire thing had to be taken apart and new fittings used because the old ones had been stretched by the tightening.

For a correct pipe thread you should be able to hand tight the fitting 3 turns, use a anaerobic pipe sealant on thread first then 4 turns with tefon tape, hand tight fitting on to pipe, wrench tight fitting 1.5 to 2 times with 14" wrench for pipe sizes 1/2" to 1" you will never get a leak, for union smear a coat of anaerobic sealent on union face, 2 to 3 turns of teflon tape on union thread tighten with 2 x 14" wrenches, 1 to tight 1 to hold against, make sure union faces butt up square, force tight but dont kill it.

I have run into many gas lines that wereliterally only hand tight with the "tefflon slick tight"on the threads.....

it works , but its not right and is sort of scarey to me..

I ran into a drip leg on a water heater last year that literally fell out in my hand when I began to loosen it.the fellow must have jsut put it in there one or two turnsand it vibrated itself outover the years.....

Put tefflon tape on the pipe if you so wish...thenPut pipe dope LIBERALLY on the male threads. just slop it on heavy , the dope is cheap and is less expensive than a leak......

then tighten down the pipe till it feels "taught"

not breaking the pipe off in the fitting , so the next poor bastardthat comes along cant ever get the pipe apart again... and not "sissy" hand tight either ..

If you really want it, I personally will only use it for very short underground runs, most plumbing supply stores will have it. The only way I will use it is if I wrap the ENTIRE pipe and fittings with the protective tape, not just the fittings and damaged areas. It is about the worst material you can use, other than unprotected pipe. It would be better if it were at least galvanized pipe with the coating.

I agree, I would not use it as a lead in water supply, either type k copper or cpvc pipe, cost wise cpvc is the best for your buck, I just installed a 80ft lead in 2" glued fittings, piping will run 160 psi in service we tested to 200 psi for 2 hrs no problems, has some issues with back fill and compacting but is clean, approved for potable water, and has a great C-factor.

I have re-done both the boiler trim and the gas line and both are now 'taught' (I like that term, and I feel it now) and completely leak-free
thanks again for all the feedback

(my rule of thumb now is 2 turns Teflon + Gasoila first 3-4 threads, roughly 7 turns total - usually about 4 turns hand tight and 3 more with a 14" wrench - I adjust as needed - some threads want another full turn, or even 2; some need a little less
but now I know what tight feels like)

What do you do if you're trying to put a T on the pipe and it needs to be aligned in a certain direction?

So if I put the fitting on hand-tite and then use a pair of wrenches (one to hold mating pipe) to tighten it, I want to ensure that it's tight but I don't want to over-tighten. Also, it has to line up in some direction.

There were several posts that reference the word "taught". I think they meant to say "taut", right?

Overtorquing a connection isn't a concern if you select the correct size wrench. For 1" down to about 1/2" use a 12" or 14" pipe wrench. The connection will be tight when you can't go any further and a significant number of threads are engaged. If you use an 18" or 24" pipe wrench it is possible to break 1" connections even if you aren't a real "husky" unit. Of course if you are making up bigger connections then it's time to pull out the big iron. I never want to see another 48" wrench.

For alignment, consider how much further it needs to be turned. If it's more than about 1/2 turn then maybe it's time to back it off and use more or less tape on the threads. Once you've done it a few times you'll get a feel for what is tight enough.

Always keep in mind the number of threads engaged. Disassemble and inspect any connections that don't engage enough threads. The joint might not leak with enough pipe dope and 2 or 3 threads engaged but the joint does not have near enough strength to be safe.

A final note on over-torquing. Listen to the joint and pay attention to the feel as you make it up. Connections may be cracked by the tapered thread and you can hear the metal break. You can also feel a change in torque (either constant or decreasing torque) as pipe begins to fail in shear.

But the 48" steel wrench almost tightens the fittings itself..
Of course, it does weigh about 50 or so lbs...LOL
Not bad if you can tighten by pulling/pushing down, but a real bear if you have to tighten by pushing UP!!